This invention relates to food casings having the property of being easily removed from food contained therein without damaging the contained food product.
Food casings employed in the processed food industry range from generally thin walled, small diameter sizes, such as for frankfurters, to thicker walled, fibrous reinforced, large diameter type casings, such as for bologna. Food casings in the form of tubes have multiple uses in that they may be employed as packaging during processing of the foodstuff encased inside, and also as protective wrappings for finished product.
In the sausage meat industry, regardless of the size of the product, part of the processing usually requires removal of the casing from the processed meat prior to final packaging or consumption. This is also true with respect to some other foods, such as certain processed cheeses, Peeling casing from processed foods, such as sausages, has presented significant problems, especially in the production of skinless frankfurters where large output is involved and efficient commercial operations require high speed automatic stuffing and peeling machines. When casings are peeled from meat, there can be a tendency for some of the meat to adhere to the casing film and be torn from the sausage within the casing. This causes loss of meat and marring of the surface of the sausage product. Such products either may not be salable, which means higher production cost, or, if offered for sale, there is usually reduced customer acceptance due to poor appearance.
In other instances, portions of the casing may not be removed at all by the machine which then requires manual intervention with resulting increased costs and reduced rate of production. In remedying the problem of casing adherence to foodstuff, several release coating compositions have been suggested for application to the interior wall of the casing for improved peelability. A few representative examples include U.S. Pat. No. 2,709,138 which discloses an internal release coating of a fatty isocyanate; U.S. Pat. No. 3,106,471 relates to release coatings of fatty ketenes; U.S. Pat. No. 2,901,358 discloses the use of a chromic chloride compound containing composition, and U.S. Pat. No. 4,062,981 teaches a water dispersible non-ionic surfactant such as sorbitan trioleate. In addition release coatings have been described which contain a water soluble cellulose ether, e.g. as described in U.S. Pat. Nos. 3,898,348 and 4,137,947. Water soluble polysaccharides have been suggested in release coatings usually in combination with a cellulose ether and a polyalkylene glycol ether.
Such know release coatings have suffered from certain disadvantages. One of the major disadvantages is that coating compositions must be prepared with precise ratios of components or there is a significant risk of poor performance. Another disadvantage is that the coating composition must be uniformly applied at a narrow range of volume per unit are of food casing. Still another problem is that the efficacy of such coatings tend to deteriorate with time. And still another problem associated with such coatings is that when casing is soaked prior to stuffing, components of the coating tend to leach from the casing altering the efficacy of the coating. This is true whether the moisture is applied by the casing manufacturer (premoisturized casing) or is applied by the meat packer. Further, known meat release coatings have had another deficiency in that the properties imparted by such coatings have had to be balanced with other desired properties of the food casing such as flexibility, strength and freedom from deterioration of the casing itself.
There is therefore a need for a unique type of release mechanism which overcomes the disadvantages previously described.
Numerous patents have been published worldwide which disclose the use of polyethylene oxide in viscose to stabilize fibers from regenerated cellulose (rayon fibers). Such additions have not been made to food casings made from regenerated cellulose, since it has not been perceived that the type of stabilization required for fibers had any application to sausage casings and further, except as noted subsequently, no advantage to adding polyalkylene glycol to viscose for the manufacture of food casing was recognized.
U.S. Pat. No. 4,198,325 discloses some effect of an N-methylol carbamate terminated polyoxyalkylene compound as a plasticizer when added to viscose in conjunction with a monocarboxylic acid-polyol ester. The addition of unmodified or otherwise modified polyalkylene glycol is not suggested for any purpose.
European Published Patent Application discloses the addition of high molecular weight (70,000 or greater) olefinic oxide to viscose for internally plasticizing film formed from the viscose to obtain various advantages. It is suggested that such addition could assist the peeling characteristics of a food casing made from the resulting regenerated cellulose. Such improvement in peeling characteristics is not nearly as good as desired. The above European Patent Application further indicates that lower molecular weight polyalkylene oxides, especially those of molecular weight 20,000 or lower, are unsuitable for addition to viscose because of leaching and reduction in product strength.